Precision potentiometers



May 30, 1967 G- J. OROZCO PRECISION POTENTIOMETERS 2 Sheets-Sheet 1Filed July 5, 1964 3 INVENTOR. Gilberf (I Orozao ATTORNEY May 30, 1967G. J. OROZCO PRECISION POTENTIOMETERS 2 Sheets-Sheet 2 Filed July 5.1964 INVENTOR. 6276px? J. Oraz c0 ATTORNEY United States PatentO3,323,093 PRECISION POTENTIOMETERS Gilbert J. Orozco, New Rochelle,N.Y., assignor to Litton Industries, Inc., Beverly Hills, Calif. FiledJuly 3, 1964, Ser. No. 380,181 6 Claims. (Cl. 338-132) This inventionrelates to otentiometers, more particularly of the stacked typeembodying two or more potentiometer resistor element assemblies in onehousing conjointly controlled by a single input shaft.

The object of the invention in general terms is to improve theconstruction and reduce the size of multi element potentiometers inwhich a plurality of potentiometer units are ganged to form a unitaryassembly for operation by a single input shaft.

In electrical apparatus employing a plurality of potentiometers forcontrol purposes, it is frequently desirable to combine two or morepotentiometers for simultaneous adjustment of the electrical functionsof the potentiometers by a single control or input shaft. If theseparate shafts of several potentiometers are coupled together byexternal mechanical coupling means, it is difficult to phase theseparate units with the required precision and an error may beintroduced as a result of play or backlash in the coupling. Even if theseparate potentiometer units are bolted or secured together foradjustment by a single input shaft, the attachment and phasing of theseparate units may present problems, such as undersirable bomplexity andcost. In any event such assemblies of the prior art are rather bulky,particularly where multi-turn potentiometers in which the input shaft isrotated through several revolutions are employed.

The present invention obviates these and other disadvantages of theprior art by a novel stacked resistor element assembly. In accordancewith the invention, the potentiometer resistor element are mountedback-to-back in a single casing and a supporting member is providedwhich overlies the resistor units and carries all of the adjustablecontact members or wipers.

An object of the invention therefore is to provide a compactconstruction which utilizes a novel rotatable contact carrier or supportcooperating with a plurality of potenti0- meter resistor elements whichmay be of the multi-turn yp Another object of the invention is toprovide a potentiometer having stable electrical and mechanicalcharacteristics, and which comprises a plurality of resistor elementseach embodying an insulating core or coil form on the outside surface ofwhich is wound a multiturn, closely spaced resistance element.

A still further object of the invention is to support the contactmembers or wipers of a multi-element potentiometer in an improvedmanner.

Still another object of the invention is to provide improved means fordampening movement or vibration of the movable contact support and themovable contacts on said support in a multi-element or stacked compoundpotentiometer.

A feature of the invention is the utilization of a cupshaped contact orwiper support for a potentiometer and an annular dampening ring engagingthe end surface of said support to dampen vibration thereof withoutimposing excessive frictional load on the rotating elements of thepotentiometer.

. In accordance with the embodiment of theinvention to be described, acompound or multi-element potentiometer having a plurality of stackedresistor units is provided with a rotatable input shaft concentric withthe insulating cores of the resistor units. Each of the resistor unitsincludes a compact core or coil form having a multiturn resistanceelement wound on the outside of the coil form. In order to obtainadjustable electrical connections to the respec tive resistor units, apivoted contact member or wiper is provided for'each of the resistorunits, said pivoted contact members being mounted on or carried by anexternal rotor or supporting member which is attached to the inputshaft. The rotor or supporting member is preferably hollow or cup-shapedand provided with slots in which the respective contact members orwipers are attached to the supporting member, the mounting of thecontact members being adjustable in order to permit phasing of saidmembers with respect to the associated resistor units. In order to avoidvibration or transverse movement of the cup-shaped support when thepotentiometer is subjected to impact or shock in service, an annularring of plastic or other suitable shock-absorbing material is mounted ina position to engage the edge of the cupshaped supporting member. Inthis manner a compact multi-element potentiometer is obtained whichpossesses stable electrical and mechanical characteristics and which isable to withstand external shock or vibration to which the poentiometermay be subjected.

The foregoing and other objects and advantages of the invention will beapparent from the following description of an illustrative embodimentthereof shown in the accompanying drawings, wherein FIG. 1 is a sideelevation, partly in section, of a multielement potentiometer havingfour stacked multiturn elements;

FIGS. 2 and 3 are end and sectional views, respectively of thecontact-supporting member or rotor shown in FIG. 1, FIG. 3 being asection taken on the line 33 of FIG. 2,-

FIG. 4 is a top view to an enlarged scale of one of the contact membersor wipers, showing the adjustable mounting of the contact member orWiper on the slotted supporting member; and

FIGS. 5 and 6 are sectional views to an enlarged scale of the contactmember and the adjacent portion of the supporting member taken on thelines 5-5 and 6-6, respectively, of FIG. 4.

Referring to the drawings, there is shown in FIG. 1 an illustrativeembodiment of the invention comprising a multi-element assembly 10composed of four multi-turn resistor elements or units 11, 12, 13 and 14mounted backto-back to form a stack on a base or hub plate 16. An inputor control shaft 17 is journaled in the base plate member 16 and ispreferably of such length that it extends through the several resistorelements, as shown. The resist-or elements 11-14 are clamped to the baseor hub 16 by a clamping ring 19 engaging the inner resistor unit 14. Theclamping ring 19 is secured by screws or bolts 21 to the rear end ofalongitudinal extension 22 of the base plate 16, said extension beingfor example in the form of a cylindrical sleeve integral with the baseplate. Obviously the resistor elements may be secured in fixed position,after being located in the desired angular relation to the input saft,by any suitable clamping or equivalent means.

The resistor elements may be compact elements of conventional characterbut, as shown, are similar to the resistor elements disclosed in thepatent of James W. Weidenman and Gilbert J. Orozco, Patent No.3,187,286, dated June 1, 1965, the disclosure of which is incorporatedherein by reference. Thus each resistor element 11-14 includes aninsulating core member or coil form 24, preferably of ceramic material,on which a helical resistance element 25 is wound with the turns inclosely spaced relation to minimize the depth or thickness of the unit.In the construction shown, a guide wire or filament 26 is wound on topof the resistance element in order to provide a guide for the contactmember or wiper 27 as shown more clearly in FIG. 4, said guide elementbeing of insulating material or consisting of an insulated wire. Thisfeature is disclosed and claimed in the prior patent to 3 James W.Weidenman and David Rathje, No. 2,871,326 dated June 27, 1959. Whileother types of resistor elements may be employed in carrying out theinvention, this construction has the advantage that the requirement fora separate mechanical feed for the adjustable contact member isobviated, thus permitting a reduction in the size and complexity of thepotentiometer.

The contact members or wipers 27 engaging each of the resistor elements11-14 are mounted on a supporting member or rotor 29 attached to therear end of the input shaft 17 and having an extension or wall portionoverlying the outside surface of the resistor elements. Thus thewipersupporting member or rotor preferably is substantially cup-shaped,with the base portion apertured to receive the input shaft to which itis clamped or fastened as by setscrews 31 and 32. In accordance withanother feature of the invention, a dampening ring 33, of plastic orother suitable shock-absorbing material, is disposed in a recess in thebase plate 16 opposite the open end of the cupshaped wiper-supportingmember 29 and engaging the edge thereof to eliminate or minimizemovement or vibration of the supporting member and of the contact wipers27 when the potentiometer is subjected to external shock or impact inservice. As shown, the dampening ring 33 may be provided with a thinprojecting edge portion 34 bearing firmly against the inner surface ofthe rotor 29 over a small area, thus insuring effective dampeningwithout imposing excessive frictional load on the input shaft.

The shaft 17 and rotor 29 attached thereto are supported for rotation inany suitable manner, as by ballbearings 37 and 38. A conventional seal39 may be provided Where necessary for the shaft 17 on the base plate16. The potentiometer itself is enclosed in a dust-cover or case 41secured to the plate 16 by screws 42. The terminal board 43 carriesterminals 44 connected to the resistors elements 11-14 in the usualmanner and through slip-rings 45 and cooperating brushes 46 to theterminals 47 (FIG. 4) of the respective wiper contacts carried by thesupporting member or rotor 29. The potentiometer is also provided withstop means to limit the rotation of the input shaft 17. As shown, thestop means 51 is of the balland-groove type described and claimed in myprior patent, No. 3,121,210 dated Feb. 11, 1964, to which reference mybe made for a detailed disclosure thereof.

As stated above, the resistor elements are shown as similar to thosedescribed in the above mentioned Patent No. 3,187,286 of James W.Weidenman et al., and include pivoted contact wipers 27 supported by therotor 29. In accordance with another feature of the invention, as shownmore clearly in FIGS. 36, the supporting member or rotor 29 is groovedas indicated at 54 to receive insulating mounting lugs 55 in alinementwith each resistor element. A series of radial slots 56 are milled inthe sleeve portion of the cup-shaped rotor 29 to provide. a space forthe wiper contacts 27. Slots 57 are provided at one edge of the slots 56to receive mounting screws 58 employed to secure the mounting lugs 55 tothe rotor 29 and to permit desired phasing adjustment of the contactwipers during assembly (see FIG. 6).

If desired, more than one aperture 56 and mounting slot 57 may beprovided for each contact wiper, four equally spaced apertures and slotsaround the periphery of the rotor 29 being shown in FIGS. 2 and 3. Thisconstruction permits the wiper to be located at any one of severalangularly spaced positions around the periphery of the rotor; or morethan one contact wiper may be employed for one or more of the resistorelements.

Any suitable type of adjustable contact or wiper may be used instead ofthat described in the patent referred to above. As illustrated in detailin FIGS. 46, the preferred construction includes a metallic bracket 61which is pivotally supported by a jewel bearing 62 in the insulatingblock 55. A flexible lead 63 connects the contact member 27 to aconductor 64 connected to a terminal 44 and clamped in position by aclamp 65. It will be apparent that the form of the wiper-supportingmember 29 and the ar rangement of a pivoted contact or wiper 27 thereonresults in a compact construction of multi-element potentiometer withoutsacrificing efficiency and reliability.

While only a single embodiment of the invention had been described indetail for the purpose of explaining the underlying principles thereof,various modifications in the form and arrangement of the componentsillustrated will occur to those skilled in the art and may be madewithout departing from the scope of the invention.

What is claimed is:

1. A multi-element potentiometer comprising an insulating core,

a plurality of multiturn resistance elements on the surface of saidcore, a rotatable contact-supporting member journaled on the axis ofsaid core and having an extension overlying the surface of saidmultiturn resistance elements, and

pivoted contact members mounted on the extension of saidcontact-supporting member, one contact member being disposed inalignment with each of said resistance elements, each of said contactmembers being independently adjustable circumferentially on saidsupporting member to alter the point of engagement of said contactmember with the corresponding resistance element.

2. A multi-element potentiometer comprising a base member, two or morestacked resistor units on said base member, each consisting of aninsulating core member and a resistance element on said core member,

"said resistor units being mounted with one resistor unit abuttingagainst said base member and another inner resistor unit behind it toform a stack,

an input shaft journaled in said base member and having the inner endthereof extending through the stacked resistor units, said base memberhaving an integral extension inside said core members of the resistorunits,

a clamping ring mounted on said integral extension and engaging the coremember of the inner resistor unit to clamp the resistor units to thebase member,

a contact-supporting member attached to the inner end of said inputshaft opposite said base member and extending over the outside surfaceof said resistor units, said supporting member being provided with aseries of separated circumferential slots, each of said slots being inalignment with one of said resistor units,

contact members adjustably mounted one in each of said series of slotsin the supporting member for phase-adjustable engagement with therespective re sistance elements to provide electrical connections tosaid elements which are simultaneously varied by the turning of theinput shaft, and

terminal connections for said resistance elements and contact members.

3. A multi-element potentiometer comprising two or more resistor units,each consisting of an insulating core member and a resistance element onsaid core member,

a base member on which said resistor units are mounted one behind theother,

means for clamping said resistor units to said base member,

an input shaft journaled in said base member and extending through saidresistor units,

a cup-shaped Contact-supporting member attached to the end of said inputshaft,

a plurality of contact members on said cup-shaped contact-supportingmember, each engaging one of said resistance elements,

means for adjustably securing said contact members on said supportingmember to permit relative phase ad= justment of each contact member withrespect to its associated resistance element, and

terminal connections for said resistance elements and said contactmembers.

4. A multi-element potentiometer comprising two or more resistor units,each consisting of an insulating core member and a multiturn resistanceelement on said core member,

a base member on Which said resistor units are mounted one behind theother, t

an input shaft journaled in said base member and extending through theresistor units,

a cup-shaped contact-supporting member attached to the end of said inputshaft spaced from said base member, said cup-shaped member beingprovided with a wall portion surrounding said resistor units,

a plurality of contact members pivotally mounted on said cup-shapedcontact-supporting member and engaging the respective resistanceelements to provide electrical connections to said elements which aresimultaneously adjusted by the turning of said input shaft,

means on said contact-supporting member for elfecting relativeindependent phase adjustment between each resistance element and itsassociated pivoted contact member, and

terminal connections for said resistance elements and said contactmembers.

5. A potentiometer comprising a base member,

a resistor unit,

a rotatable input shaft journaled in said base member and extendingthrough said resistor unit,

a contact-supporting member attached to the end of said input shaft andconsisting of a base portion and a substantially cylindrical wallportion surrounding said resistor unit and projecting from the baseportion of said supporting member, a

a contact member pivotally mounted on the wall portion of saidcontact-supporting member and engaging said resistor unit, and

an annular plastic ring mounted in fixed relation to said base memberand engaging the periphery of the Wall portion of saidcontact-supporting member for damping the resulting movement orvibration of said member when the potentiometer is subjected to shock orimpact during use.

6. A multiple-element potentiometer comprising a plurality of resistorunits, each consisting of an insulating core member and a multiturnresistance element on the outer surface of said core member,

a base member on which said resistor units are mounted one behind theother,

an input shaft journaled in said base member,

a cup-shaped contact-supporting member having a substantiallycylindrical Wall portion surrounding said resistor units, saidcontact-supporting member being attached to said input shaft and havingthe wall portion thereof provided with a plurality of circumferentialslots spaced in both axial and circumferential directions,

a plurality of contact members mounted on said contact-supporting memberand engaging the respective resistor elements,

means for pivotally and adjustably mounting said contact members in theslots of said contact-supporting member, and

a plurality of terminals conductively connected to said resistanceelements and said contact members, respectively.

References Cited UNITED STATES PATENTS 2,599,126 6/1952 Reed 336-440 X2,657,295 10/1953 Barclay 33 8132 2,686,634 8/1954 Kolisch 338l30X2,974,299 3/ 1961 Youngbeck 33 81 63 3,011,142 11/1961 Mair 338-132X3,187,286 6/1965 Weidenman 338149 RICHARD M. WOOD, Primary Examiner.

I. G. SMITH, Assistant Examiner.

6. A MULTIPLE-ELEMENT POTENTIOMETER COMPRISING A PLURALITY OF RESISTORUNITS, EACH CONSISTING OF AN INSULATING CORE MEMBER AND A MULTITURNRESISTANC ELEMENT ON THE OUTER SURFACE OF SAID CORE MEMBER, A BASEMEMBER ON WHICH SAID RESISTOR UNITS ARE MOUNTED ONE BEHIND THE OTHER, ANINPUT SHAFT JOURNALED IN SAID BASE MEMBER, A CUP-SHAPEDCONTACT-SUPPORTING MEMBER HAVING A SUBSTANTIALLY CYLINDRICAL WALLPORTION SURROUNDING SAID RESISTOR UNITS, SAID CONTACT-SUPPORTING MEMBERBEING ATTACHED TO SAID INPUT SHAFT AND HAVING THE WALL PORTION THEREOFPROVIDED WITH A PLURALITY OF CIRCUMFERENTIAL SLOTS SPACED IN BOTH AXIALAND CIRCUMFERENTIAL DIRECTIONS, A PLURALITY OF CONTACT MEMBERS MOUNTEDON SAID CONTACT-SUPPORTING MEMBER AND ENGAGING THE RESPECTIVE RESISTORELEMENTS, MEANS FOR PIVOTALLY AND ADJUSTABLY MOUNTING SAID CONTACTMEMBERS IN THE SLOTS OF SAID CONTACT-SUPPORTING MEMBER, AND A PLURALITYOF TERMINALS CONDUCTIVELY CONNECTED TO SAID RESISTANCE ELEMENTS AND SAIDCONTACT MEMBERS, RESPECTIVELY.